Factor management of metrics updates into its own class.

chrome/browser/page_load_metrics/page_load_metrics_update_dispatcher.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UPDATE_DISPATCHER_H_
+#define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UPDATE_DISPATCHER_H_
+
+#include <map>
+
+#include "base/time/time.h"
+#include "chrome/common/page_load_metrics/page_load_metrics.mojom.h"
+
+namespace content {
+class NavigationHandle;
+class RenderFrameHost;
+}  // namespace content
+
+namespace page_load_metrics {
+
+class PageLoadMetricsEmbedderInterface;
+
+namespace internal {
+
+// Used to track the status of PageLoadTimings received from the render process.
+//
+// If you add elements to this enum, make sure you update the enum value in
+// histograms.xml. Only add elements to the end to prevent inconsistencies
+// between versions.
+enum PageLoadTimingStatus {
+  // The PageLoadTiming is valid (all data within the PageLoadTiming is
+  // consistent with expectations).
+  VALID,
+
+  // All remaining status codes are for invalid PageLoadTimings.
+
+  // The PageLoadTiming was empty.
+  INVALID_EMPTY_TIMING,
+
+  // The PageLoadTiming had a null navigation_start.
+  INVALID_NULL_NAVIGATION_START,
+
+  // Script load or execution durations in the PageLoadTiming were too long.
+  INVALID_SCRIPT_LOAD_LONGER_THAN_PARSE,
+  INVALID_SCRIPT_EXEC_LONGER_THAN_PARSE,
+  INVALID_SCRIPT_LOAD_DOC_WRITE_LONGER_THAN_SCRIPT_LOAD,
+  INVALID_SCRIPT_EXEC_DOC_WRITE_LONGER_THAN_SCRIPT_EXEC,
+
+  // The order of two events in the PageLoadTiming was invalid. Either the first
+  // wasn't present when the second was present, or the second was reported as
+  // happening before the first.
+  INVALID_ORDER_RESPONSE_START_PARSE_START,
+  INVALID_ORDER_PARSE_START_PARSE_STOP,
+  INVALID_ORDER_PARSE_STOP_DOM_CONTENT_LOADED,
+  INVALID_ORDER_DOM_CONTENT_LOADED_LOAD,
+  INVALID_ORDER_PARSE_START_FIRST_LAYOUT,
+  INVALID_ORDER_FIRST_LAYOUT_FIRST_PAINT,
+  INVALID_ORDER_FIRST_PAINT_FIRST_TEXT_PAINT,
+  INVALID_ORDER_FIRST_PAINT_FIRST_IMAGE_PAINT,
+  INVALID_ORDER_FIRST_PAINT_FIRST_CONTENTFUL_PAINT,
+  INVALID_ORDER_FIRST_PAINT_FIRST_MEANINGFUL_PAINT,
+
+  // New values should be added before this final entry.
+  LAST_PAGE_LOAD_TIMING_STATUS
+};
+
+extern const char kPageLoadTimingStatus[];
+
+}  // namespace internal
+
+// PageLoadMetricsUpdateDispatcher manages updates to page load metrics data,
+// and dispatches them to the Client. PageLoadMetricsUpdateDispatcher may delay
+// dispatching metrics updates to the Client in cases where metrics state hasn't
+// stabilized.
+class PageLoadMetricsUpdateDispatcher {
+ public:
+  // The Client class is updated when metrics managed by the dispatcher have
+  // changed. Typically it owns the dispatcher.
+  class Client {
+   public:
+    virtual ~Client() {}
+
+    virtual void OnTimingChanged() = 0;
+    virtual void OnMainFrameMetadataChanged() = 0;
+    virtual void OnSubframeMetadataChanged() = 0;
+  };
+
+  // The |client| instance must outlive this object.
+  PageLoadMetricsUpdateDispatcher(
+      Client* client,
+      content::NavigationHandle* navigation_handle,
+      PageLoadMetricsEmbedderInterface* embedder_interface);
+  ~PageLoadMetricsUpdateDispatcher();
+
+  void UpdateMetrics(content::RenderFrameHost* render_frame_host,
+                     const mojom::PageLoadTiming& new_timing,
+                     const mojom::PageLoadMetadata& new_metadata);
+
+  void DidFinishSubFrameNavigation(
+      content::NavigationHandle* navigation_handle);
+
+  const mojom::PageLoadTiming& timing() const {
+    return *(current_merged_page_timing_.get());
+  }
+
+  const mojom::PageLoadMetadata& main_frame_metadata() const {
+    return *(main_frame_metadata_.get());
+  }
+  const mojom::PageLoadMetadata& subframe_metadata() const {
+    return *(subframe_metadata_.get());
+  }
+
+ private:
+  using FrameTreeNodeId = int;
+
+  void UpdateMainFrameTiming(const mojom::PageLoadTiming& new_timing);
+  void UpdateSubFrameTiming(content::RenderFrameHost* render_frame_host,
+                            const mojom::PageLoadTiming& new_timing);
+
+  void UpdateMainFrameMetadata(const mojom::PageLoadMetadata& new_metadata);
+  void UpdateSubFrameMetadata(const mojom::PageLoadMetadata& subframe_metadata);
+
+  // Merge values from |new_paint_timing| into |pending_merged_page_timing_|,
+  // offsetting any new timings by the |navigation_start_offset|.
+  void MergePaintTiming(base::TimeDelta navigation_start_offset,
+                        const mojom::PaintTiming& new_paint_timing,
+                        bool is_main_frame);
+
+  void DispatchTimingUpdates();
+
+  // The client is guaranteed to outlive this object.
+  Client* const client_;
+
+  // Interface to chrome features. Must outlive the class.
+  PageLoadMetricsEmbedderInterface* const embedder_interface_;
+
+  // Time the navigation for this page load was initiated.
+  const base::TimeTicks navigation_start_;
+
+  // PageLoadTiming for the currently tracked page. The fields in |paint_timing|
+  // are merged across all frames in the document. All other fields are from the
+  // main frame document. current_merged_page_timing_ contains the most recent

[Charlie Harrison, 2017/05/24 21:02:51]

|current_merged_page_timing_| and elsewhere in this comment.

[Bryan McQuade, 2017/05/25 02:30:21]

done

+  // valid page load timing data, while pending_merged_page_timing_ contains
+  // pending updates received since current_merged_page_timing_ was last
+  // updated. pending_merged_page_timing_ will be copied to

[Charlie Harrison, 2017/05/24 21:02:52]

"updated to the client" maybe? There are multiple notions of updating here (this
class gets updates but also dispatches updates).

[Bryan McQuade, 2017/05/25 02:30:21]

used 'dispatched to the client'

+  // current_merged_page_timing_ once it is valid, at the time the
+  // Client::OnTimingChanged callback is invoked.
+  mojom::PageLoadTimingPtr current_merged_page_timing_;
+  mojom::PageLoadTimingPtr pending_merged_page_timing_;
+
+  mojom::PageLoadMetadataPtr main_frame_metadata_;
+  mojom::PageLoadMetadataPtr subframe_metadata_;
+
+  // Navigation start offsets for the most recently committed document in each
+  // frame.
+  std::map<FrameTreeNodeId, base::TimeDelta> subframe_navigation_start_offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(PageLoadMetricsUpdateDispatcher);

[Charlie Harrison, 2017/05/24 21:02:51]

#include "base/macros.h"

[Bryan McQuade, 2017/05/25 02:30:21]

done

+};
+
+}  // namespace page_load_metrics
+
+#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UPDATE_DISPATCHER_H_